Published Japanese Patent No. 2782711 discloses an internal combustion engine equipped with a supercharger having a function of raising the pressure of the intake air introduced into a cylinder to increase the output power. The supercharger equipped with electric motor has an electric motor built therein, and the output shaft of the electric motor constitutes the rotary shaft of the supercharger.
In the internal combustion engine disclosed in this Japanese Patent No. 2782711, the difference between the intake pipe pressure (boost pressure) corresponding to accelerator position and the current intake pipe pressure (boost pressure) detected by an intake pipe pressure (boost pressure) sensor provided in an intake passage is computed, and if it is determined that the difference is larger than a predetermined value, the electric motor is activated to increase the rotation speed of the rotary shaft of the supercharger to a desired rotation speed.